The epitaph for Lovie Smith's tenure as head coach of the Bears could read, "He couldn't fix the offense."

For all the good things Smith did in his nine years in Chicago, his undoing was his inability to take care of the side of the ball in which he had no background.

The Bears fired Smith on Monday after a 10-6 season, Tribune sources have confirmed. They started 7-1 but fell apart down the stretch, mostly because they couldn't score.

Since Smith took over in 2004, the Bears have ranked higher than 23rd in offense only once. They have ranked 28th or lower four times.

Smith tried four offensive coordinators during his Bears career. His first thought was to run a similar offense to the one he was familiar with when he was defensive coordinator of the Rams, so he hired Terry Shea.

The Bears finished last in the league in offense behind quarterbacks Chad Hutchinson, Craig Krenzel, Jonathan Quinn and Rex Grossman, and Shea was dismissed after one season.

Smith then turned to Ron Turner for his second stint as Bears offensive coordinator. Turner lasted five years in what was the heyday for Smith's offense.

It was during this period that Smith's stubborn allegiance to Grossman became an issue. "Rex is our quarterback," he said over and over again.

Those days Smith often talked frequently about how the Bears "get off the bus running," and the team achieved its offensive identity by pounding the ball with Thomas Jones, then Cedric Benson and finally Matt Forte.

But after the Bears traded for Jay Cutler in 2009 and they still finished 23rd in offense and missed the playoffs, Turner was made the scapegoat and fired.

An extensive job search that included interest in Jeremy Bates, Rob Chudzinski and Tom Clements led the Bears back to Smith's old friend Mike Martz, for whom he had worked in St. Louis. Going from the conservative Turner to the aggressive Martz was quite a philosophical shift for Smith.

Martz's offense sputtered in 2010 but started to come on the next season. Then Cutler broke his thumb in the 10th game, and the team unraveled. The Bears lost five straight, and Martz was fired along with general manager Jerry Angelo, the man who brought Smith to Chicago.

Smith's next move was to go conservative again, this time by promoting offensive line coach Mike Tice. A first-time play caller, Tice made great use of new acquisition Brandon Marshall but struggled to find other reliable targets or to overcome protection issues.

The Bears finished 28th in offense.

The only time Smith enjoyed a fairly efficient offense was in 2006, when the offense ranked 15th in a season that ended in the Super Bowl.

Defensively, the Bears were on the other end of the spectrum under Smith. With perennial Pro Bowlers Brian Urlacher and Lance Briggs as the constants, Smith's defenses usually were among the best in the NFL.

Since 2004, the Bears defense ranks first in the league in takeaways, three-and-out drives forced and third-down percentage and is fourth in scoring defense.

Smith's defenders scored 34 touchdowns, which became a signature of the Bears' style of play.

It was Smith's defense that drove the Bears to their first Super Bowl appearance in 21 years after the 2006 season. Smith and Tony Dungy became the first two African-Americans to coach a Super Bowl team as the Bears took on the Colts.